DESCRIPTION: To date, neither the usage patterns nor the health risks of e-cigarettes are well known. The purpose of this project is to determine the effects of nicotine concentration and flavor additives in e-cigarettes on the preferences, cognitions, affects, and behaviors associated with e-cigarette use, particularly in women of reproductive age. We suspect that women, compared to men, will be more motivated to smoke by negative effects, rather than by nicotine level, and will have a greater preference for sweeter or masking flavors. These findings may have implications for future regulation of alternative tobacco products, particularly if certain flavors or nicotine concentrations are associated with greater use. To explore these issues, we will conduct a two- phase study of e-cigarettes with 120 male and female smokers who report no intention to quit smoking. Phase I will entail a laboratory baseline test of preferences, liking satisfaction, and effects on craving using high versus low concentrations of nicotine crossed with tobacco-flavored or sweet/masking flavor additives. During this phase subjects will identify a most preferred e-cigarette flavoring. Phase II will evaluate subjects' usage patterns of preferred cigarettes and of e-cigarettes in their home environments, employing the same subjects studied in Phase I. Subjects in Phase II will be followed using a daily interactive voice response (IVR) assessment procedure for a period of 1 week, and instructed to smoke as they normally would. After this period subjects will be asked to refrain from smoking cigarettes, randomized to one of four e-cigarette conditions, and followed with the IVR procedure for 6 weeks. The e-cig conditions will be: No nicotine - tobacco flavoring; High nicotine - tobacco flavoring; No nicotine - preferred flavoring; High nicotine - preferred flavoring. During the IVR periods subjects will call the IVR system each evening to answer questions about daily cigarette or e-cigarette use, nicotine cravings before and after e-cigarette use, e-cigarette liking, affects and cognitions related to use, and situational determinants of using the e-cigarette. During the e- cig period subjects also will be asked about use of regular cigarettes despite being asked not to smoke, and cigarette smoking will be tested weekly. Analyses of e-cigarette usage rates will be adjusted for taste sensitivity. A 3-month follow-up will be used to determine if cigarette smoking habits are altered by the e- cigarette experience. Results will provide information about daily motivations to use cigarettes and e- cigarettes, the influence of flavors and nicotine levels on consumption of alternative tobacco products like e- cigarettes, and the effects of using e-cigarettes on subsequent cigarette smoking.